AUTHOR=Zhao Chungui , Zhang Yi , Chan Zhuhua , Chen Shicheng , Yang Suping 

TITLE=Insights into arsenic multi-operons expression and resistance mechanisms in Rhodopseudomonas palustris CGA009

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00986

DOI=10.3389/fmicb.2015.00986

ISSN=1664-302X

ABSTRACT=<p>Arsenic (As) is widespread in the environment and causes numerous health problems. <italic>Rhodopseudomonas palustris</italic> has been regarded as a good model organism for studying arsenic detoxification since it was first demonstrated to methylate environmental arsenic by conversion to soluble or gaseous methylated species. However, the detailed arsenic resistance mechanisms remain unknown though there are at least three arsenic-resistance operons (<italic>ars1, ars2</italic>, and <italic>ars3</italic>) in <italic>R. palustris</italic>. In this study, we investigated how arsenic multi-operons contributed to arsenic detoxification in <italic>R. palustris</italic>. The expression of <italic>ars2</italic> or ars3 operons increased with increasing environmental arsenite (As(III)) concentrations (up to 1.0 mM) while transcript of <italic>ars1</italic> operon was not detected in the middle log-phase (55 h). <italic>ars2</italic> operon was actively expressed even at the low concentration of As(III) (0.01 μM), whereas the <italic>ars3</italic> operon was expressed at 1.0 μM of As(III), indicating that there was a differential regulation mechanism for the three arsenic operons. Furthermore, <italic>ars2</italic> and <italic>ars3</italic> operons were maximally transcribed in the early log-phase where <italic>ars2</italic> operon was 5.4-fold higher than that of <italic>ars3</italic> operon. A low level of <italic>ars1</italic> transcript was only detected at 43 h (early log-phase). Arsenic speciation analysis demonstrated that <italic>R. palustris</italic> could reduce As(V) to As(III). Collectively, strain CGA009 detoxified arsenic by using arsenic reduction and methylating arsenic mechanism, while the latter might occur with the presence of higher concentrations of arsenic.</p>